Effects of ultrasonic pretreatment and drying approaches on the drying kinetics and rehydration of sprouted mung beans

Abstract Sprouting is one of the most traditional methods used to decrease most of the antinutritional elements in legumes. The assistance of ultrasound appears to enhance the drying step of the sprouted legumes. The aim of this study was to examine the influence of ultrasound pretreatment and drying methods (hot‐air and infrared) on the drying time, mass transfer kinetic, effective moisture diffusivity (Deff), and rehydration ratio of sprouted mung beans. The ultrasound process (40 kHz and 150 W) was performed in an ultrasonic bath for 0, 5, 10, 15, and 20 min. The results showed that the ultrasonic pretreatment increased the moisture diffusion capacity (higher moisture loss) and reduced the drying time of sprouted mung beans. Also, the drying time of samples in the infrared dryer was significantly less than that in the hot‐air dryer (p < .05). The Deff determined by Fick's second law was varied from 1.36 × 10−10 to 1.88 × 10−10 m2 s−1, and from 1.18 × 10−9 to 1.85 × 10−9 m2 s−1, for samples dried in hot‐air and infrared dryers, respectively. Comparing the coefficient of determination (r), sum of squared error (SSE), and root mean squared error (RMSE) values of 10 models, it was concluded that the Midilli model represents the drying characteristics of sprouted mung beans better than the others. The rehydration ratio of dried samples in hot‐air and infrared dryers increased when the ultrasound pretreatment time was increased. In general, the use of ultrasound pretreatment (about 20 min) and an infrared dryer is a promising drying technique for sprouted mung beans with higher mass transfer and a shorter drying time

Modeling of moisture loss kinetics and color changes in the surface of lemon slice during the combined infrared-vacuum drying

Color is one of the most important appearance attributes of food materials, since it influences consumer acceptability. In this study the effects of combined infrared-vacuum drying on the drying kinetics, moisture diffusivity, surface changes (shrinking) and color changes kinetics of lemon slices were investigated. Both the infrared lamp power and vacuum pressure influenced the drying time of lemon slices. The regression results showed that the quadratic model satisfactorily described the drying behavior of lemon slices with highest R value and lowest SE values. The effective moisture diffusivity increased from 2.92 × 10−10 and 1.58 × 10−9 m2/s when the infrared lamp power was increased from 300 to 400 W. The colour parameters L∗ (lightness), a∗ (redness/greenness), b∗ (yellowness/blueness), and ΔE (total colour difference) were used to estimate colour changes during drying. L∗, a∗ and b∗ values of dried lemon increased during drying. The rise in infrared power has a negative effect on the ΔE and with the increase of infrared radiation power it was increased. Different kinetic models were used to fit the experimental data and the results revealed that the power model was the most suitable to describe the color change intensity (ΔE). Keywords: Colour parameters, Image processing, Infrared drying, Kinetic, Lemo

Effects of ultrasound time, xanthan gum, and sucrose levels on the osmosis dehydration and appearance characteristics of grapefruit slices: Process optimization using response surface methodology

In this work, the novel use of ultrasonic pre-treatment and edible coating treatment during osmosis dehydration to optimize the weight reduction, moisture loss, sucrose gain, rehydration, and surface shrinkage using a response surface methodology (RSM) based on a central composite design (CCD) technique was successfully conducted on grapefruit slices. The process parameters include sonication pre-treatment time (5–10 min), xanthan-gum-based edible coating (0.1%-0.3%, w/w), and sucrose concentration (20–50 Brix), were examined and optimized for osmosis dehydration of grapefruit slices. At each step, three grapefruit slices were immersed in an ultrasonic water bath at 40 kHz, 150 W, and 20 C. Then, the sonicated slices were placed in a container contain sucrose and xanthan, and the container was put in a 50 C water-bath for 1 h. The optimum concentration of xanthan gum, sucrose, and time of treatment were predicted to be 0.15%, 20.0 Brix, and 10.0  min, respectively. Under this optimum condition, estimated values of response variables are as follows: weight reduction 14.14%, moisture loss 25.92%, solids gain 11.78%, rehydration ratio 203.40%, and shrinkage 2.90%. The weight reduction and moisture loss increased when the sonication time and sucrose concentration increased. Results demonstrated that the experimental data could be adequately fitted into a linear model with p-value ranging from 0.0001 to 0.0309 for all the variables examined. The rehydration of dried samples increased when xanthan concentration increased. Also, the weight reduction, moisture loss, sucrose absorption, and shrinkage declined with increasing in the xanthan levels

Effects of edible coatings and ultrasonic pretreatment on the phenolic content, antioxidant potential, drying rate, and rehydration ratio of sweet cherry

The target of this study was to examine the influence of ultrasound pretreatment and edible coatings (xanthan, guar, and wild sage seed gums) on the total phenols content, antioxidant potential, mass transfer rate, effective moisture diffusivity (Deff), and rehydration rate of sweet cherries (SC). For the edible coating of SC, a 0.2% gum solution (xanthan, guar, and wild sage seed) was prepared and the SC were dipped into the aqueous solution. Also, the ultrasound process (40 kHz and 150 W) was performed in an ultrasonic bath for 3 min. The gums coating increased the total phenols content, antioxidant properties, and drying time and decreased the Deff values. The highest value of DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging activity (61.04 ± 2.09%) was observed on coated SC by guar gum. The mean drying times for uncoated, xanthan gum-coated, guar gum-coated, and wild sage seed gum-coated SC were 130, 160, 175, and 140 min, respectively. In this study, the SC Deff as determined by the second Fick law varied from 1.39 × 10−9 m2/s to 2.46 × 10−9 m2/s. The Midilli model gave the best results for describing single-layer drying of SC. The mean rehydration ratio for uncoated, xanthan gum-coated, guar gum-coated, and wild sage seed gum-coated SC were 141.81, 167.26, 176.21, and 156.87 %, respectively. Considering the total phenols content, antioxidant activity, and rehydration ratio, edible coating and ultrasonic pretreatment will be more promising for SC pretreatment before drying and other processes

Influence of organic acids on the viscosity and rheological behavior of guar gum solution

The present study aims to determine the influence of four edible organic acids (ascorbic, citric, malic, and tartaric) at two concentrations (0.5, and 1 %) on the viscosity and rheological behavior of guar gum dispersion (0.2 %, w/v). The finding of this study revealed that the apparent viscosity of guar gum dispersions reduced when the shear rate increased. Additionally, the apparent viscosity of the guar gum dispersions reduced as the organic acids concentration increased from 0 to 1 %. The highest decrease in viscosity was related to 1 % ascorbic acid and the lowest was related to 0.5 % malic acid. The rheological behavior of dispersions were successfully modeled using Power law, Bingham, Herschel-Bulkley, and Casson models, and the Power law model was the best one for describing the behavior of guar gum dispersions containing organic acids. The Power law model showed good performance with the maximum r-value (mean = 0.9988) and least sum of squared error (SSE) values (mean = 0.0021) and root mean square error (RMSE) values (mean = 0.0119) for all samples. The consistency coefficient (k-value) values of the samples (Power law and Herschel-Bulkley models) reduced as the acid percent was increased. The sample containing 1 % tartaric acid had the lowest k-value and the sample containing 0.5 % ascorbic acid had the highest k-value. The flow behavior index (n-value) (Power law and Herschel-Bulkley models) of the samples increased when the acid percent was increased. In summary, the use of guar gum in food products containing high concentrations of tartaric and ascorbic acids is not recommended

Production and evaluation of total phenolics, antioxidant activity, viscosity, color, and sensory attributes of quince tea infusion: Effects of drying method, sonication, and brewing process

This study aimed to examine the influence of drying approaches (convective and infrared (IR)), sonication, and brewing time on the total phenolic content (TPC), antioxidant activity (AA), viscosity, color indexes, and sensory attributes of quince tea infusion (QTI). The AA and TPC in the QTI dried in the IR dryer were higher than in the convective dryer. The TPC and AA of QTI prepared by convective and IR dryers increased when the ultrasound treatment and brewing time were increased. In terms of viscosity and Brix, there was no differences between the QTIs and the average viscosity and density of the samples were 1.79 ± 0.28 mPa.s and 3.18 ± 0.07°Brix, respectively. The QTI prepared by the IR has a reddish-brown hue (higher a* value), but the samples prepared with the convective dryer were yellow (higher b* value). The sensory attributes scores of QTI prepared by IR were higher than those of convection-dried samples. In general, the use of an IR dryer for drying grated quince, ultrasound treatment for 8 min, and brewing time for 30 min is a promising condition for the production of QTI with higher TPC and AA, and with appropriate color and sensorial acceptance

Effect of chitosan‐based coatings enriched with savory and/or tarragon essential oils on postharvest maintenance of kumquat (Fortunella sp.) fruit

The present study assessed the ability of chitosan‐based coatings incorporating savory and/or tarragon essential oils (EOs) to preserve the postharvest quality of kumquats. Changes in weight loss, titratable acidity, total soluble solids, and vitamin C content were determined over 30 days of storage at 7°C. Savory (Satureja hortensias L.) essential oil was characterized by thymol (29.1%), carvacrol (26.6%), and γ‐terpinene (24.72%) as major constituents. While, in the tarragon (Artemisia dracunculus L.) essential oil, estragol (81.89%), β‐cis‐Ocimene (4.62%), and β‐trans‐Ocimene (3.44%) were the main ones. The CH‐EOs coatings were effective in reducing weight loss of kumquats fruits during storage. Moreover, the tested composite coatings showed positive effects in maintaining vitamin C and fruits treated with CH‐oil coatings retained good sensory acceptability. The obtained results demonstrate the potential of the combined application of chitosan and savory and/or tarragon EOs as a promising postharvest treatment for maintaining the postharvest quality of kumquats fruits